Preparing Hard Drive for new OS

I want to install XP Pro. I currently have 2k pro. How do I put everything I have on a CD to save all my data. Do I have to go to each individual file or is there a way to copy everything on the hard drive all at once? I want to do it the fastest but best way to ensure I don't lose anything in case I want to put part of it on the xp or all of it on another hard drive. Is it possible to transfer an operating system directly from one hard drive to another. If I get another computer with a better hard drive can I transfer the xp to the new computer, if so how? I'm fairly new to getting into the more advanced computing. But I'm finding it fascinating and want to learn more. I want to be able to do most anything I want on my own, to be able to go into any files, drives etc and know what it does. I'm like a sponge and really want to learn much more about how this thing works. But I also don't want to get ahead of myself and do more harm than good. So all help and advice is most welcome. The ole Sarge is going to see if he has what it takes or can an old dog learn new tricks?? Thanks guys